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SH2 domain-containing inositol-5'-phosphatase-1 (SHIP1) inhibits inflammation by hydrolyzing phosphoinositide-3'-kinase generated membrane phosphatidylinositol-3,4,5-trisphosphate (PIP3). Bioinformatic analysis of SHIP1 from multiple species revealed a pleckstrin homololgy-related (PH-R) domain, which we hypothesize mediates SHIPI's association with the membrane, a requirement for its biological function. Recombinant murine SHIP1 PH-R domain was subjected to biophysical and biochemical analysis. Residues K370 and K397 were found to be important for PH-R domain association with membrane PIP3. Wild-type PH-R domain bound PIP3 with 1.9 ± 0.2 nM affinity, while the affinity of a K370A/K397A substituted mutant was too low to measure. Wild-type (but not the K370A/K397A substituted) full-length SHIP1 protein, reconstitutes normal inhibition of Fcγ receptor-mediated phagocytosis when introduced into SHIP1-/- murine macrophages, reducing the number of phagocytic events by 2-fold as compared to SHIP1-/- cells. In fact, the PH-R-mediated membrane interaction appears to be a major mechanism by which SHIP1 is recruited to the membrane, since the K370A/ K397A substitution reduced the recruitment of both full-length SHIP1 and the PH-R domain by ≥2-fold. We have previously shown that SHIP1 enzyme activity can be targeted for therapeutic purposes. The current studies suggest that molecules targeting the PH-R domain can also modulate SHIP1 function. [ABSTRACT FROM AUTHOR]